AU620701B2

AU620701B2 - Body electrode and process for producing it

Info

Publication number: AU620701B2
Application number: AU51822/90A
Authority: AU
Inventors: Walter Schmid
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-02-27
Filing date: 1990-02-26
Publication date: 1992-02-20
Anticipated expiration: 2010-02-26
Also published as: ATE113453T1; EP0413802A1; CA2028106A1; EP0413802B1; AU5182290A; WO1990009758A1; CA2028106C

Abstract

A body electrode contains one or more galvanically active sensors connected on the body contact side with a layer (4) of electrically conductive, adhesive, elastic, hydrophilic material which adheres to the skin. The side of the sensor(s) facing the skin and the layer adhering to the skin are covered with a non-adhesive protective layer (5). The two said layers each consist of a castable polymer which is cast in a mould and then cured. The electrode can be manufactured economically by casting without stamping.

Description

insert place and date of signature.

Signature of declarant(s) (no attestation required) Note: Initial all alterations.

4. The basic application....referred to in paragraph 3 of this Declaration were the first application.S made in a Convention country in respect of the invention the subject of the application.

Declared at Pfcaffenhofefl this 5th day of November 1990 DAVIES COLLISON, MELBOURNE and CANBERRA.

4

L

S II -a-%WV I TflflCAW11Z INTl AMN.OLNCEMNt OF THE LAME INt (AND, WHERE APPLICABLE, SI ?'PUBL ITION OFAMENDED CLAIMS ,BE DI ATEMENT UNDER ARTICLE 19) VIESENS (PCT) (00 Internationale Veroffentlichingsnunmmer WO 99I/09758 Al (43) Internationales Veriffentlichungsdatum: 7, September 1990 (07.09.90) (51) Interrnationale Patentkiassiflkation 5 A61B 5/0408 (21 f internationales Aktenzeichen: PCT/EP90/00320 (22) Inernationales Anmeldedatuni: 26. Februar 1990 (26,02.90) Prioritiitsdaten: P 39 06071,3 P 39 06 0i74.8 27. Februar 1989 (27,02.89) 27. Feti ruar 1989 (27.02.89) (81) Bestir-smungsstaaten: AT (europflisches Patent), AU, BE (europilisches Patent), CA, CH (europflisches Patent), DE (europliisches Patent), DK (europliisches Patent), ES (europflisches Patent), FR (europllisches Patent), GB (europflisches Patent), IT (europlisches Patent), LU (europilisches Patent), NL (europlisches Patent), SE (europilisches Patent), Vfw611lcntlicht Mit internationleni Ruchcrcheribericu, Mit gciderwen Ansprichcn.

Veriffentlicsungstlatuni der gelinderten Anspriiche: 4, October 1990) (04.10.90) Apiuelder und Erfinder: SCHM ID, Walter [DE/DE]; F'ichsweg 9, D-7914 Pfaffenhofen/ Roth (DE).

(74) Arwalt: DEUFEL, Paul, Deufel, Sch~n, H-ertel, Lewald, Isartorplatz 6, Postfach 26 02 47, D-8000 Mflnchen 26

(DE),

(54) Tith. BODY ELECTRODE AND PROCESS FOR PRODUCING IT (54) Bezeichming., KORPERELEKTRODF UND VERFAHREN ZU IHRFR HERSTELLUNG (57) Abstract A body electrode contains one or more galvanically active sensors connected on the body contact side with a layer of' electrically conductive, adhesive, elastic, hydrophilic material which adheres to the skin. The side of the sensor(s) facing the skin and the layer adhering to the skin are covered with a non-adhesive protective layer The two said layers each consist of' a castable polymer which~ is cast in a mould and then cured, The electrode can be manufactured economically by casting without stamping.

(57) Zusamnmerfassung Eine Kbrperelektrode enthilt eirien odw- mebrere galvanisch aktlve Sensor(en), dee (die) an der Kbrperkontaktseite mit einer auf der Haut haftenden Schicht aus eilieem elektrlsch letZ.-den kiebenden elastischen hydrophilen Material verbunden ist (sind), wobei die dem Kbrper abgewandte Seite des Sensors bzw. der Sensoren und die auf der Haut haftende Schicht mit .iner nichtklebenden Deckschicht abgedeckt sind, Die beiden genannten Schichten bestehen Jeweils aus einem vergiessbaren Polymer, welches in eine Form gegossen und anschliessend ausgehtlrtet worden ist. Unter Vermeidung von Stanzvorgllngen =kann die Elektrode durch Vergiessen in wirtscha~tlicher Weise hergestelit werden.

j~4V The invention relates to a body electrode and a process for its manufacture.

Such electrodes are known (see, for example, U.S.

Patents No. 4,554, 92& and 4,066,078 and 4,362,165 as ,ell as DE-AS 28 14 061, DE-OS 35 07 301 and WO 81/02097). They are fastened to the skin of the patient to be examined or treated and serve the purpose of transmitting electrical signals from the body to a recording instrument, or in the other direction, signals from a device to the body. They are used, for example, to record electrocardiograms, as ground electrodes in oper'atiorns, or to mitigate pain through transmission of electrical pulses.

These electrodes essentially comprise one or more generally plate-shaped galvanically active sensor(s) which have a place of attachment for an electrical conductor leading to a recording device or transmitting electrical pulses -om a device into the body. The sensor is connected .n its body contact side to a layer capable of adhering to the skin and consisting of an electrically conductive, adherent, elastic hyd ophilic material or combinations of material. This layer serves the rDurpose of ensuring firm adhesion of the body electrode to the skin while smoothing out unevenesses of the body to make certain of transmission of electrical sigrdls from the body by way of the sensor to a display unit or of a signal generated in an instrument by way of the sensor into the body. On the side of the sensor facing away from the body there is a U l 0k*, 't non-conductive elastic and non-adhesive layer which is a covering or supporting layer and which covers the electrode and the layer that adheres to the body (in case this layer is larger than the electrode plate) and is connected to the electrode plate.

Electrodes of this kind are thus m'anufactured by stamping parts in the desired size and shape from a wide continous strip of the adhesive layer which comes in contact with the skin, a sensor then being applied to the preform obtained, and finally a covering and supporting layer (also produced by being stamped out) is applied in alignment onto the layer that has contact with the skin if this layer is larger in area than the sensor plate. Considerable problems arise in stamping out the first layer which adheres to the skin, because it is difficult to remove the stamped adhesive parts from the stamping tool.

Due to the adhesiveness of the strip from which the parts of the layer which adheres to the skin are stamped, difficulties arise in the stamping procedure as the stamped out parts tend to adhere to the stamping tool, so that it is difficult to carry out high-speed continuous stamping.

Hence, the invention was set the task of developing a body electrode which can be produced by avoiding the stamping processes.

Furthermore, it was set the task of developing a procedure -or ti,e manufacture of body electrodes that can be odf-ducted in a trouble-free and cost-effective manner,

I

,q I, 4 According to the present invention there is provided a body electrode comprising: an electrically conductive, elastic hydrophilic first layer capable of adhering to the skin; one or more galvanically active sensor(s) connected to the first layer on the side having contact with the body; and a non-conducting, non-adhesive covering layer covering the side of the sensor(s) and the layer adhering to the skin facing away from the body; wherein the first layer and the covering layer each comprise a castable polymer which is cast in a mold and then hardened.

15 According to a further aspect of the present invention there is provided a process for manufacturing a body electrode as described above, wherein the layer adhering to the skin and the covering layer are each manufactured with a castable polymer which is cast into a mold and then hardened.

:As the problem of adhesion while stamping out the S" parts of the layer adhering to the skin no longer exists in the process claimed for the invention, it can be conducted on a commercial scale continuously, troublefree and at high speed.

It is advisable for the ratio of the area of the first layer adhering to the skin to the area of the plate-like sensor or sensors to be higher than one, and in particular two or three. That is, it is advisable to use the smallest possible sensor in relation to the \p LIA 911212,EEDAT.008,a:\51822sch.res,4 c-4 S

I

first layer that adheres to the skin. This arrangement is particularly expedient if, according to a further preferred form of the invention, both the layer adhering to the skin and the covering layer are transparent so that observation is possible of the skin contact surface on the patient undergoing treatment. It can thus be determined whether skin irritations occur, especially when the electrode is applied for long periods of time.

The layer adhering to the skin expediently comprises a conductive natural and/or synthetic material, in particular a polymer material, which for example can be an elastomeric polymer or a collagen.

Furthermore, this layer can comprise a non-conductive natural or synthetic material, that contains an electrolyte to produce conductivity. It may also be expedient for the layer adhering to the skin to contain a tackifying agent, a plasticiser (softener) and/or hygroscopic agent, so that in this way the adhesive properties, elastic properties and the hygroscopicity may be customized.

The covering layer preferably comprises a natural or synthetic non-conductive material which is expediently a polymer, preference being given to elastomers or collagens.

The layer adhering to the skin and the covering layer may comprise the same materiel. The layer adhering to the skin must naturally be rendered conductive by the addition of an electrolyte, as well f '3 i -1 7T i( 6 as adherent. The adhesiveness can be achieved by addition of a tackifying agent or, in the event that cross-linkable polymers are used to produce the two layers, by making the layer coming in contact with the skin less heavily cross-linked than the covering layer in the event that polymers in a less heavily crosslinked state are sufficiently adhesive.

According to another preferred embodiment of the invention, if the layer adhering to the skin and the covering layer are transparent, the body electrode of the invention may have an intermediate transparent layer bearing symbols, for example, either captions or graphic images. In this way it is possible to identify the electrode from the viewpoint of its origin.

The body electrodes according to the invention may contain one or more sensors and preferably be round or square in shape, but they can also be produced in any other shapes.

All known sensors are suitable for the body electrode of the present invention, for example, those described in DE-OS 24 59 627, U.S. Patents No.

4,554,924 and 4,066,078, in DE-AS 28 14 061 and DE-OS 29 35 238. A plate-like sensor equipped with a pushbutton type of connection for an electric lead has proved to be especially suitable. This plate-like sensor is made of plastic and is coated with a conductive, galvanically active material such as a silver/silver chloride layer. The sensors may also preferably comprise polymers which represent a reversible redox system. Such types of material are known.

i k1i 0 it 7 Generally speaking, although a plate-like sensor which is mostly round is employed in the body electrode of the invention, but it is also possible to employ as a sensor the conductor or conductors of the electric lead or leads by means of which signals are transmitted to a recording device. In this particular costeffective embodiment, an electric lead with a silver conductor which is coated with a silver chloride layer, is preferably employed.

In addition, microspheres made of synthetic material and coated with zinc or silver can, for example, be used as galvanically active sensors, such as the materials marketed under the brand name of Metalite. A suitable number of these microspheres are positioned between the layer coming in contact with the skin and the covering layer, and are connected with an electric lead which leads to a recording device.

The sensors and/or electric leads may also comprise layers which have been applied to a foil, for example with screen printing.

If a plate-like sensor is used in the electrode of the invention, the plate element preferably has recesses, in particular holes, which ensure better, holding for the layer having contact with the skin and/or the covering layer.

It is also possible to transmit electric signals received from the body tc, a recording device by a wireless method. For this purpose the electrode may be fitted with an integrated circuit as transmitter

U

characterized by low power consumption and energized by hLi power source such as a round cell.

0t i lop si l otanmt eet i inl i i 8 If the electrode of the invention is to be applied on the thorax, for example, it is advisable that the electrode should be elastic in the longitudinal direction. In this case, an embodiment of a body electrode is provided which comprises several electrode units connected by sheeting folded in an accordion-like arrangement that allows for the electrode's longitudinal expansion due, for example, to enlargement of the thorax caused by breathing.

The invention is illustrated in detail by the accompanying Figures 1 8. Identical parts in each drawing have been given the same reference numbers.

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 shows a vertical section through an embodiment of the electrode of the invention with a sensor.

is a top view of the electrode of the invention provided with three sensors.

is a top view of another embodiment of such an electrode.

is a top view of an embodiment of such an electrode whoch is fitted with a transmitter.

is a top view of an electrode of the invention designed as a stimulation electrode.

is a vertical section through an electrode of the invention which is extendible longitudinally.

is a top View of a ring-shaped electrode of the invention with a sensor provided with holes in its plate element.

Figure 6 Figure 7 if I)i L J .i li; r I-if I i i 9 The embodiment of the electrode of the invention as shown in Figure 1 comprises a plate-like round sensor 1 with a wiring point for an electric lead which leads to a recording device. The sensor may comprise one of those described in the references cited above.

Or. its side facing the body, the sensor is provided with a layer 4 that adheres to the skin, and which may comprise any known elastic, mild to the skin, nontoxic, hydrophilic and natural or synthetic material capable of adhering to the skin. A prerequisite for this material is that it must be castable in any form.

The material in question preferably comprises a synthetic, and preferably elastomeric polymers or a polymer mixture and/or a collagen. This material is either co;nductive or rendered conductive by addition of an electrolyte. The layer 4 is produced by preferably using synthetic organic polymers or polymer mixtures which are either intrinsically conductive or rendered conductive by the addition of an electrolyte. These polymers must be castable in the form of a solution, a melt, or a prepolymer of suitable low viscosity. An abundance of polymers meeting these requirements are available. Polymer' suitable for conducting are, for example, those described in U.S. Patent No. 4,066,078 of 2-acryl-amido-2-met hylpropane sulfonic acid, its salts, copolymers of the named acid, copolymers of the acid's salt, and mixtures thereof in mixtures of water, alcohols and mixtures thereof; polymers described in DE-OS 29 35 238 with, at least 5 mol monomer Units which contain a salt of a carboxylic acid; conductive polymer compounds in question which consist of a hydrophilic cross-linked polymer and a hydrophilic noncross-linked polymer and are described in EP 85 327.

U3*

W

Among the polymers which are not conductive as such and are rendered conductive by t-ea addition of an electrolyte, are polyvinyl alcohols, polyvinyl acetates, polyvinyl proprionates and polyvinyl ethers such as are described, for example, in Adhesion 5/81, Pages 208-213, as well as polyacrylates and polymethacrylates such as those cescribed in DE-OS 31 36 366, U.S. Patent No. 4,554,924 and in DE-AS 28 14 061.

The unsaturated acrylate resin types marketed by BASF under the brand name of "LAROMER" have been found to be particularly useful, special preference being given to the resirn that is marketed under the brand name "LAROMER EA-8812".

To increase or control adhesiveness, these polymers may additionally contain one or more tackifying agents such as the glycidyl ether acrylates and their derivatives known to be suitable for this purpose. In addition, they may contain plasticizers (softeners) and/or hygroscopic agents, i.e. polyols, such as diols and triols, for example hexane triols, polyethylene glycol etc. It is expedient that the polymers contain an additive of baoteriostatics and odor absorbing agents such as eucalyptol.

As has already been noted, the polymers employed to produce the layer 4 coming in contact with the skin are cast in a castable state in a mold, either in the form of a solution, a melt or a prepolymer hardenable by cross-linking. The latter embodiment is preferred.

i 11 The hardening is preferably accomplished by irradiation with ultraviolet light and/or heat by the use of Known photoinitiators and/or hardening accelerators. Examples of suitable compounds include per compounds such as peroxides and/or ketone hardening accelerators, for example 2-hydroxy-2-methyl-1-phenyl-propan-l-on, which is an efficient photoinitiator for acrylated epoxides, acrylated polyurethanes, acrylated polyethers and arylated unsaturated polyesters or mixtures thereof.

The adhesive, conductive and elastic properties of the layer 4 having contact with the skin can be customized by varying the type and amount of conductive polymers employed, either naturally conductive ones or ones rendered conductive by the addition of electrolytes, and also of any tackifying agent, plasticizer and/or hygroscopic agent employed, and also of the degree of cross-linking and hardening.

Preferably alkali halides such as potassium chloride are used as electrolytes to render nonconductive polymers conductive for production of the layer 4 that comes in contact with the skin.

The material for the covering layer 5 may be any known natural and/or synthetic hydrophilic material which is also castabl.e in the form of a scilution, a melt or a cross-linkable or" hardenable prepolymer and which bonds with the material of the layer 4 on solidification. The material i'or the covering layer must of course not be conductive and also must not contain additives rendering it conductive. As with the layer having contact with the skin, the layer may also be transparent. The many known materials meeting the /s $J 0~, 1,i 12 specified requirements include, among others, polymers, especially elastomeric polymers, gelatins, especially ossein with a gelatin strength of 60 to 260 Bloom and a cast gelatin Shore hardness between 40 and 90 Shore, as well as in particular the polyacrylates used to produce the layer 4, but which are cross-linked or hardened to the extent that they are no longer adhesive. Hence, in accordance with the invention, preference is to be given in the manufacture of the covering layer 5 to the use of the same polyacrylate prepolymers employed in the manufacture of the layer having contact with the skin, but which are cros:- linked or hardened to a greater extent so that they are no longer adhesive.

This results in an especially strong bonding of the polymers in the layer 4 and the layer In the embodiment shown in Figure 1, an irvtermediate layer 7 provided with symbols is positioned between layer 4 that has contact with the skin and the covering layer 5. As with layers 4 and the intermediate layer 7 consists of transparent material so that the symbols can be recognized while examining the electrode. This intermediate layer also consists of a castable natural or synthetic material, and the same material may be used as for production of the layers 4 and 5. However, the intermediate layer 7 must not bt conductive.

In addition, symbols may be applied to the upper side of the covering layer S facing away from the body, for example by imprinting, pasting on, c'r painting. It is advisable, however, that any embossed symbols are applied to the upper side of the covering layer 5 and have been obtained by casting the covering layer in a rE %lZsq,.

rt'

I

form with appropriate indentations. In this case the body electrode is not produced, as described later, by casting the layer having contact with the skin, applying the sensor and then casting the covering layer. Instead the process is carried out in the reverse order.

The layer adhering to the skin is provided with a detachable protective layer 6 which may consist of any material that is separable from the layer adhering to the skin, and which is water repellant and/or is provided with a releasing coating such as a silicone coating. It is particularly expedient that the protective coating 6 consists of the mold in which the body electrode has been produced by casting the layers 4 and 5, and if appplicab layer 7. That is, the body electrode is not removed from the mold after castinq but is marketed as a unit with this casting mold. The casting mold is then removed when the electrode is in use. The covering layer preferably has a tab (not shown) to assist in easier removal from the mold.

The body electrode according to the invention and which is shown in Figure 2 is rectangular in shape and contains three circular sensors. But in this case, the electrical conductors with which the sensors may be connected to a display unit, are not connected with the sensor at a push-button type wiring point as in the case of the embodiment shown in Figure 1. Instead, they are fastened to the sensors without press-button type of connecting device and are embedded in the horizontal plane of the body electrode in the covering layer and project from its lateral edge. These irlectrical conductors 11 may consist of conventional connecting 0yUj leads, but they preferably consist of carbon fibres and/or conducting plastics.

,11 cl manufactured with a castable polymer which is cast into a mold and then hardened.

1-1 14 a connecting tab 17 from which point conneection to a recording device is possible. In the case of this recesses 14 which are filled with a conductive adhesive materie.F such as is used to produce the layer adhering to the skin. Sheeting 13 coated in areas 15 with a galvanically active layer is applied to this structure.

The sheeting 1haleads 11 which are also applied by coating. Coating of this sheeting 13 with the zalvanically active layer or with the electricAl leadsss may, for example be carried out with the screenprirating process.

Figure shows an embodiment sirilar to that in Figure 3 but in this case the electrical leads ei are connected to a tran mitter 9 powered by a round cell 16. The transmitter 9 forwards by wireless means signals transmitted from the body to a recording device.

Figure 4 shows an electrode according to the invention which may be used as a stimulation electrode with polarity selectable as required. This electrode comprises a cast coverig layerd 5 with recesses in S which the material for the layer 4 adhering to the skin is cast, and galvanically active sensors I with the appropriate ei,-otrical leads 11 which are in contact Iwith the layer 4 adhering to the skin ar, applied or the sheeting 13 corresponjinG to the embodiment shown in Figure 5 An electrode such as this Is used to transmit signalsy enerated ir a device, Toh example, to yrniti<gate pain.

4f j i- (57) Zusammenfassung Eine K6rperelektrode enthlt einen oder mehrere galvanisch aktive Sensor(en), der (die) an der K6rperkontaktseite mit einer auf der Haut haftenden Schicht aus einem elektrisch leitenden klebenden elastischen hydrophilen Material verbunden ist (sind), wobei die dem Karper abgewandte Seite des Sensors bzw. der Sensoren und die auf der Haut haftende Schicht mit einer nichtklebenden Deckschicht abgedeckt sind. Die beiden genannten Schichten bestehen jeweils aus einem vergiessbaren Polymer, welches in eine Form gegossen und anschliessend ausgehfirtet worden ist. Unter Vermeidung von Stanzvorgangen kann die Elektrode durch Vergiessen in wirtschaftlicher Weise hergestellt werden.

Figure 6 shows an electrode exteindible in the longitudinal direction 18 Which comprises several individual electrodes. It comprises four individual electrodes which are connected on the sides of their covering layer 5 by sheeting 10 folded like an accordian. The foil used preferably consists f a plastic, espeially elastomeric plastic, which can be folded without causing cracks. The four sensors of this electrode may be connected to a display unit with the leads 11. Th sensor 1 in this emrbodiment, and also the embodiment shown in Figure 1, may comprise a strip of a salvanically active metal or a plastic that is coated with a galvanically active metal. This strip projects in angled form through the center of the covering layer and may be connected to a display unit by an electric lead.

Figure 7 shows a top vie of a bory electrode which rincipally corresponds to that shown in ctiure 1. The plate of the circular electrode is provided with holes 8 to ensure better anchoring both in the layer coming in contact with the skin (not shown) and the covering layer 5. When the electrode plate is applied to the freshly cast layer adhering to the skin and when the covering layer 5 is cast, the holes are penetrated by the respective materials thereby achieving a good anchorage. This electrode has a tab 19 on its covering layer side to facilitate removal from the mold.

The thickness of the layer 4 having contact with the skin for the eribodiments of flat formed body electrodes as described above ranges preferably between 800 pm and 2,500 uim, and with particular preference for 1,000 um to 2, r0o um, whereas the thickness of the "i electrical sigr-als from the boay Dy way ui .I1 o to a display unit or of a signal generated in an instrument by way of the sensor into the body. On the side of the sensor facing away from the body there is a

U

16 covering layer 5 ranges preferably between 500 um and 2,500 Um, especially between 1,000 pm and 2,000 um.

Circular electrodes of the embodiments shown in Figure 1 and Figure 7 have diameters preferably between 20 mm and 60 mm.

The thickness of the electrode plate of the plate-like electrodes employed in these electrode units ranges preferably between 50 pm and 1,500 pm, especially between 80 pm and 1,000 pm.

An additional embodiment of an electrode of the present invention consists of a contact cap which is preferably to be applied to the head and used for EEG recording, as shown in Fi-ure 8.

This contact cap comprises a cone-shaped contact body 20, open at its wider end, and is produced by casting from a non-adhesive, conductive material into which a sensor 1 is fi ted and holds the contact tbdy firm by a clamping force. This contact cap is fastened on the parts of the body that are to be monitored, preferably the head, by the use of adhesive tape or the like.

For protection of the contact body 20, it may be manufactured and marketed with the mold in which it was cast as a protective layer.

The layer having contact with the skin is produced by casting the above named polymers in a castable state in a cast, that is to say either in the form of a solution, a melt, or a prepolymer that is hardenable by cross-linking.

L

can be conducted in a trouble-free and cost-effective manner.

K-I

t

I

Y~~

I

Ii, I 17 The material to be used for manufacturing the protective or covering layer may be any natural and/or synthetic hydrophilic material, especially polymeric material which is also castable in the form of a solution, a melt, or a cross-lirikable or hardenable prepolymer, and in manufacture cc.mbines with the material of the layer having contact with the skin. The material for the covering layer must naturally not be conductive and not contain any additives which may render it conductive, and as with the material of the layer having contact with the skin, may also be transparent. The polymers to be used in the process of the present invention have been mentioned at the beginning.

Corresponding to a preferred embodiment of the process o'f the present invention, in case either the layer adhering to the skin and/or the covering or protective layer (especially the latter) comprise a transparent material, a preferably transparent layer with symbols may also be provided between these two layers. The symbols consist, for example, of capcions or graphic images in order to identify the electrode's origin or application.

The material to be used for the possible manufacture of the intermediate layer provided with symbols can also comprise a Qastable, naturel or synthetic material. The same materials may be used as are employed for manufacturing the layers having contact with the skin and the covering layers. However, the intermediate layer must not be conductive.

il

I

18 The sensors employed for carrying out the process of the present invention are essentially known and are also described in the above named literature.

Identification of the electrodes produced in accordance with the invention is also possible by engraving in the mold symbols or captions (such as company manufacture data or type designations) with the aid of a die in reflected type. The covering or protective layer will be cast first. The electrodes produced in this way are then provided with embossed formed symbols on the surface of the covering or protective layer.

In the following, the process according to the invention will be described with reference to synthetic, elastomeric, polymer materials which will be employed for the manufacture of the layer adhering to the skin and the covering or supporting layer of an electrode. The electrode comprises: a layer having contact with the skin; a plate-like sensor with a connecting point for an electric lead (the sensor plate's surface being smaller than the surface of the layer having contact with the skin); and a covering or protective layer that covers the sensor plate and the side facing away from the body of the layer having contact with the skin.

The process according to the invention may, as already mentioned, be carried out in such a way that a melt is produucd from the polymer employed for forming a layer adhering to the skin. With the aid of a metering device, this melt will be continually fed in such quanttities into the mold, which corresponds to the AS I d 7! Io -k- 19 size and design of the layer having contact with the skin, so that the desired thickness of the layer will be achieved. After the melt has at least cooled or by and large solidified, so that by applying the sensor it

I

skin, the sensor is set down on the layer that has been the desired thickness from a downstream metering device.

It is also possib.le to use a polymer solution in a suitable solvent for casting the layer forming a skin. In this case, the solvent is allowed to evaporate after casting the layer, accelerated if necessary by warming, sufficiently at least sc that the sensor which is applied does not sink undesirably deep into the layer that is formed.

It is that this cross-linking or hardening may be carried out by heat, light, ionizing radiation, or with the use of catalysts, or initiators or hardening and polymerization accelerators. Combinations of these methods may also be employed, whereby each method also complies with the type of polymer material that is used.

Catalysts, initiators or hardening or accelerating agents are added to the casting solution immediately- before casting, as is expedient.

Another method is possible, according to the invention, Whereby a castable state of a cross-linkable or hardenable preliminary stage o the polymer to be used is cast. After casting and before setting the 2 ly tha is f,.

v v preferably comprise polymers which represent a reversible redox system. Such types of material are known.

sensor, it is expedient at least to sufficiently crosslink or harden so that the cast layer is no longer so soft that the sensor may penetrate it too deeply.

According to one of the three named methods, the covering or supporting layer is also cast. However, any one of the methods that is followed for this layer must not be identical with the method according to which the layer adhering to the skin has been cast.

It is especially expedient, however, that the same cross-linkable or hardenable preliminary stages of the polymer are employed for manufacturing both the layer adhering to the skin as well as the covering or supporting layer. The covering or supporting layer, which should no longer be tacky, is more heavily crosslinked according to one or more of the na med methods, than theherring t the skin, which must remain tacky.e cross-linkTe oing may be carried out in the described way.

The casting mol dused to apply the process according to the invention is preferably produced bY deep-drawing sheeting in the desired shape and depth.

Hence, for the purpose of industrial production molds situated side by side and one after the other are produced by deep-drawing from a strip of material that does nriot combine with the material of the layer adhering to the skin, btt can be detached from this layer rather easily and without leaving residues. These molds are then brought in succession under metering devices at the speed corresponding to that at which the devices in question operate, for feeding the castable

K

wireless method. For this purpose the electrode may be fitted with an integrated circuit as transmitter characterized by low power consumption and energized by L4 power source such as a round cell.

21 material for the layer adhering to the skin. The irradiation and/or heating devices by means of which the crosslinking or hardenino reactions can be carried out or accelerated may be installed downstream from the metering devices.

The materials for the strip from which the molds for casting the body electrode of the invention are deep-drawn, preferably comprise a water-repellant polymer, or a polymer having a coating of an antiadhesive or release agent such as a water-repellent silicone. Metal foils such as aluminium foils are also suitable.

It is suitable that the mold in which the body electrode has beer, produced by casting in accordance with the invention, may be used as a protectve layer in order that the layer adhering to the skin is protected from damage or drying out. In this case, the electrode and the mold emp ;d to manufacture it is marketed as one unit.

A variant of the process of the invention is that the layer adhering to the skin is cast in a casting mold and hardened, a sensor with electric connection facility is introduced, and finally the covering or supporting layer is cast with the sensor embedded.

Another variant of the process of the invention corrprises introducing into a casting mold sheeting on all or part of which a galvanically active layer has been deposited by a screen printing process for exarple, and in specific configurations if necessar'y.

|dt Figure 7 is a top view of a ring-shaped electrode of the invention with a sensor provided with holes in its plate element.

rE1 22 The layer adhering to the skin is cast on this sheeting in contact with the galvanically active layer, and a covering sheet is placed over it after solidification.

In the event of the manufacture of such a body electrode, the glvanically active layer may be connected to a reco-'ding instrument by introducing into the mold connecti ig leads which project prior to casting either from the side of the layer having contact with the skin or upwards from the electrode.

They may then be connected by way of leads to the recording instruments.

However, the leads may also be applied, similarly to the galvanically active layer, in the form of a layer on the ;heeting to be introduced into the casting mold, prefert.bly in a thickness of 30 um to 200 Um. It is advisable for these leads to end in a tab on the electrode, from which point they can then be connected to the recording instrument by a conventional electric lead.

In conclusion, reference may be made to several preferred embodiments in respect of formirig and manufacturing electrodes: The layer 4 adhering to the skin and the covering layer 5 are transparent, the electrode itself is circular or square, the layer 4 adhering to the skin is from a conductive natural and/or synthetic polymer, in particular from a noni-conductive polymer, which contains an electrolyte, The covering layer 5 is from a non-conductive natural or synthetic polymer, the layer rr i -l V L. II I 11IS 4 0 IU 4 ISI cross-linked polymer and are described in EP 85 327.

M i

-II

23 4 adhering to the skin is provided with a removal protective coating 6. This protective coating may consiat of the mold in which the electrode has manufactured by casting. The layer adhering to the a in and the covering layer 5 are transparent, and between both these layers there is a trasnparent layer 7 which is provided with s/mbols. The sensor or sensors 1 are provided with a connecting point 3 for electric leads 11, and the sensor or sensors 1 may even be the conductor of the electric leads 11. The sensors 1 are plate-like and have recesses 8, the sensor or sensors 1 may be connected with a transmitter 9. The body electrode may contain several sensors 1, and finally the body electrode may be extendible in a longitudinal direction.

The following example illustrates the invention: A mixture of 100 g l-vinyl-2-pyrrolidone, 10 g hydrogen peroxide by weight solution in water), 7 g a.-(hydroxyethoxy) phenyl-(2-hydroxy-2-propyl) -ketone, g polyetheracrylate, 15 g polyvinylpyrrolidcne, 100 g propanetriol, 20 g distilled water, 4 g triethanolamine and 5 g ammonium hydroxide (10% in water) was produced.

g of a solution of 30 g potassium chloride and 5 g sodium tetraborat in 100 g water were added to this mixture.

The layers crfiing in contact with the skin were cast from the mixture obtained to a thickness of 500 um in a deep-crawn circular casting rmolds of siliconecoated polyethylene sheeting with a diameter of 50 mm and a depth of 3 mm. The cast layers were irradiated .for a period of 15 seconds with ultraviolet light and Sheated to a tempelature of 60 0

C.

A.III~I, 21s Then a round plate-- lke sensor having a diameter of 6 rfmr and a sensor plat~e depth- of 1 mm 'was applied to this layer.

Then a transparent mixture of 60 g propanediol, g- glv-cide etheracrylate, 40 g tripropyleneglycoi diacrylate, 60 g polyethylene a-lycol-300, and .3 g 2hydroxy-2--rmethyl,-1-ht-eylproaLrie----onie was cast as covering layer, to a thickness of 800 ijm on the strU~:Lire obtained, and hardened b/ the action of ultraviolet light for a period of 15 seconds at nz temperature Of 600C.

The body electrode thereby obtained was transpar'ent ir, the places not covered by the sensor, plate and adhered well to human skin without exerting any irritating effects.

The reference numer ,is in the following claims do not in any way limit the scope of the respective claims.

Claims

1. A body electrode comprising: an electrically conductive, elastic hydrophilic first layer capable of adhering to the skin; one or more galvanically active sensor(s) connected to the first layer on the side having contact with the body; and a non-conducting, non-adhesive covering layer covering the side of the sensor(s) and the layer adhering to the skin facing away from the body; i wherein the first layer and the covering layer each comprise a castable polymer which is cast in a mold and S* then hardened.

2. A body electrode as claimed in claim 1, wherein the Sratio of the area of the layer adhering to the skin to the area of the sensor or sensors is greater than 1. S3. A body electrode as claimed in claim 2 wherein the ratio of the area of the layer adhering to the skin to the area of the sensor(s) is from 2 to 3.

4. A body electrode as claimed in any one of claims 1 to 3, wherein the first layer contains a tackifying agent, a plasticizer and/or a hygroscopic agent. A body electrode as claimed in any one of the previous claims, wherein the first layer and the covering layer comprise the same cross-linkable, non-conductive polymer, and the polymer of the covering layer is more heavily cross-linked.

6. A body electrode as claimed in any one of clais 1 to 5, wherein the sensors and/or electrical leads comprise layers of galvanically active material which have been applied to sheeting. 'h area oft9e121seEEDATs008sa:\f1822mitres325 -26-

7. A body electrode as claimed in claim 6 wherein the layers of galvanically active material are applied to sheeting by soreen printing.

8. A process for manufacturing a body electrode as claimed in any one of claims 1 to 7, wherein the layer adhering to the skin and the covering layer are each manufactured with a castable polymer which is cast into a mold and then hardened.

9. A process as claimed in claim 8, wherein a melt, solution or a crosslinkable or hardenable preliminary stage of the material to be cast is used for casting the layer adhering to the skin and the covering layer. So A process as claimed in claim 8 or claim 9, wherein the cast layer adhering to the skin and the covering layer are transparent and a layer provided with symbols, which may also be transparent, is fitted between these two layers. S

11. A process as claimed in any one of claims 8 to wherein the layer adhering to the skin is cast and hardened in a casting form, a sensor with electric connection capability is introduced, and then the covering layer is cast with the sensor embedded in it.

12. A process as claimed in any one of claims 8 to 11, wherein sheeting with an applied galvanically active layer is introduced into the mold that is used for manufacturing the electrode and the layer adhering to the skin is cast above the gslvanically active layer. k9I2 0I N 91121ZEEDAT.008,a: 51822s res,26 in Figure 3. An electrode such as this i6 used to transmit signals generatedq in a device, tor example, to J. itigate pain. 27

13. A body electrode as claimed in claim 1 and/or a process as claimed in claim 8 substantially as hereinbefore described with reference to any one of the drawings or the example. DATED this 12th day of December,, 1991. WALTER' SCHMID By His Pateidt Attorn :ys DAVIES COLLISON CAVE 0 Go. 0 4, 0# 0 0 0 911212,EEDAT.68a:\5822scb.rs,27