FR3072561A1 - ELASTOMER CONTACT PAD FOR ELECTRODES - Google Patents

Abstract

The invention relates to a flexible contact pad made of elastomer for an electrode for collecting an electrophysiological signal (2), said pad comprising: - an upper part (12) comprising elastic clamping means (13) of said pad on said electrode, a concave-shaped lower part (11) comprising a skirt (15) intended to maintain in a cavity (14) an electrolyte gel cushion between said electrode and a support, said skirt being provided with a peripheral sealing lip ( 18) curved inward to provide a sealed connection of said lower portion with said support. The invention also relates to a device for medical or veterinary use for electrophysiological examination, particularly for the production of encephalograms.

Description

Technical field of the invention

The invention relates to the field of diagnostic or medical or veterinary stimulation electrodes, more specifically the invention relates to a contact pad made of flexible elastomer to equip electrodes for electro-physiological collection and medical stimulation such as electrocardiograms ECG, electroencephalograms EEG , EMG electromyograms, having an opening for the establishment, maintenance and distribution of the conductive gel between said electrode and the epidermis of the subject.

The invention can also be used for man-machine interfacing applications (neuro-piloting of robots, vehicles, exoskeletons, etc.), muscle stimulation of the bio-feedback type and functional rehabilitation.

Prior art

Electrophysiological examinations: ECG electrocardiograms, EEG electroencephalograms, EMG electromyograms and in particular electroencephalography (EEG), use very low signal currents and variations which can be parasitized by poor contacts and by the variation of the conductivity parameters in the time.

Several types of electrodes are known from the prior art for electrophysiological readings, in particular flexible self-adhesive composite electrodes for single use or repositionable (US3713435), metal electrodes (FR2356402).

The vast majority of electrophysiological examinations are carried out using 25-metal electrodes based on silver and conductive creams or gels in order to ensure good electrical conductivity between said electrodes and the patient's epidermal tissues.

Such electrodes are for example described in US Pat. No. 6,574,513, which describes electrode assemblies for electroencephalograms, or in US Pat. No. 6,201,982, which describes a system for attaching an electrode comprising a gel sponge that conducts the patient's hair.

These electrodes are used naked in direct contact with the skin or with a conductive fluid (for example a conductive sticky paste, a conductive liquid gel, a moisturizing cream containing abrasive particles, etc.) or dressed using a foam or textile sleeve in order to maintain a moist, flexible and conductive interface by absorbing a little conductive gel. These textile or sponge covers for the electrodes are called "infants".

These "infants" bring an improvement in the quality of the recordings and a certain comfort for the patient, because the electrodes must keep a good contact and are held in place thanks to different elastic devices.

However, the porous nature of the foams or textiles used to make these so-called "baby" covers does not guarantee optimal maintenance of the conductive gel during long recordings, because the gel oozes and evaporates. This can cause loss of signals and distort recordings. The drying phenomenon is amplified by the capillary drainage effect of the hair and by the absorption of the skin.

To compensate for this drying-out phenomenon, certain operators of electrophysiological examinations are tempted to increase the quantity of conductive gel, but this solution presents the risk of generating measurement errors. In fact, if the conductive gel of one electrode comes into contact with the gel of other electrodes, an electrical continuity is formed and the measurements of potential differences between these electrodes are falsified.

Furthermore, the spongy nature of these covers makes them difficult to clean between two examinations and their replacement is not easy. As it dries, the conductive gel forms solid residues in the form of crystals which foul and harden the babies. In practice, we see that they are too rarely replaced, making hygiene questionable and open to criticism.

Subject of the invention

The present invention relates to a tampon made of elastic material, of the elastomer type and of class compatible with medical or veterinary use, having an improved shape and a texture of flexibility ideal for optimizing and making reliable the electrical contacts between an electrode and an epidermal support. . The material and the geometry of the contact pad according to the invention make it possible to remedy the drawbacks listed above of the devices of the prior art.

5Summary of the invention

The invention relates to a flexible contact pad (1) made of elastomer for an electrode for collecting an electrophysiological signal (2), said pad comprising:

an upper part (12) comprising elastic clamping means (13) of said pad on said electrode, a lower part (11) of concave shape comprising a skirt (15) intended to hold in a cavity (14) a gel cushion electrolyte between said electrode and a support, said skirt being provided with a peripheral sealing lip (18) curved inwardly making it possible to ensure a sealed connection of said lower part with said support.

Preferably, the contact pad is for medical or veterinary use and said support is the epidermis of a human or animal subject.

Preferably, the elastomer is a grade silicone compatible with medical or veterinary use.

The contact pad may further include a mounting interface (20) of plastic, polymer or metal allowing adaptation to different types of electrodes.

The contact pad may include a central valve maintained by a pierced membrane that can be mounted on an electrode having a central bore to allow gel injection.

The said concave lower part may include a complementary elastomer structure allowing local differential pressures to be exerted on the epidermis.

In one embodiment, said lower part of concave shape comprises one or more additional concentric sealing lips.

In another embodiment, said lower part of concave shape comprises an internal membrane (17) pierced with holes and furnished with flexible pins (16).

The pad can be covered on the surface with a layer of flexible conductive resin or a conductive metal film, preferably by vapor deposition.

The elastomer can be a conductive elastomer, preferably an elastomer containing 10 nano carbon nanowires or silver nanowires.

The elastomer may include conductive microfibers that are flush with the surface.

The contact pad can be manufactured by injection, vulcanization or three-dimensional printing.

The invention also relates to a device for medical or veterinary use for electrophysiological examination comprising at least one electrode for collecting an electrophysiological signal and at least one contact pad as described above assembled by elastic clamping on said electrode, in particular for carrying out electroencephalograms.

The invention also relates to a network of contact pads as described above linked together by a flexible elastomer membrane.

List of Figures

Figure 1: Sectional view of the contact pad according to the invention assembled on the electrode

Figure 2: 3D view of a contact pad - electrode - electrode holder assembly 30 Figure 3A: Sectional view of the contact pad - Embodiment with flexible pins

Figure 3B: 3D view of the contact pad - embodiment with flexible pins.

Figure 4: 3D view of the contact pad with mounting interface.

Detailed description of the invention

The figures are presented for illustration and not limitation.

5 Figure 1 represents a contact pad (1) according to the invention in flexible elastomer assembled on an electrode (2) of electro-physiological collection or of medical or veterinary stimulation, such as ECG, EEG. The contact pad includes a concave lower part enabling the conductive gel to be put in place, maintained and distributed between said electrode (2) and the subject's epidermis.

Figure 2 shows a 3D view of a contact pad-electrode-electrode holder assembly. The contact pad encloses the base of the electrode (2), the upper part of the electrode (2) is mounted on an electrode holder (3).

FIGS. 3A and 3B show the detailed geometry of the contact pad according to the invention, in an embodiment comprising a structure provided with flexible pins in the concave lower part.

The upper part (12) of the contact pad is designed to hang firmly by elastic deformation on the electrode for collecting the electrophysiological signal or on a holding interface allowing the storage or cleaning of the contact pad outside periods of 'use. This elastic clamping connection also provides local sealing to prevent gel from escaping around the electrode. In FIG. 3A, the bead (13) maintains the pad by elastic clamping on the electrode.

The lower part of the concave-shaped contact pad (11) comprises a flexible peripheral skirt (15) with a balloon effect, which provides a filling and holding volume for the gel.

The cavity (14) formed by the skirt (15) is filled with electrolyte gel maintained and protected from the air by said peripheral skirt (15).

The curved lip (18) towards the inside of the skirt (15) brings to the system an auto-plating effect by the internal pressure transmitted by the gel on the skirt. This geometry gives a gel cushion effect during installation and the pressure exerted on the gel promotes the penetration of moisture into the hair fibers and tissues.

The contact pad according to the invention, made of elastomer, preferably silicone, may be provided in its lower part with a structure promoting contact with the epidermis of the subject. The embodiment shown in FIGS. 3A and 3B is that in which the contact pad is provided with a complementary elastomer structure making it possible to exert local differential pressures on the epidermis, here flexible pins (16) on a internal membrane (17) pierced with holes.

FIG. 3B shows a 3D view of said contact pad according to the invention provided with an additional elastomer structure allowing local differential pressures to be exerted on the epidermis, namely flexible pins (16) on an internal membrane ( 17) pierced with holes.

Figure 4 depicts the embodiment in which the contact pad is mounted on a mounting interface (20) enclosing a smaller electrode.

The elastic nature of the elastomer constituting the buffer allows it to a certain extent to be fixed on different sizes of electrodes or mounting interfaces.

The contact pad according to the invention made of elastic material, for example of the elastomer type of nature and class compatible with medical or veterinary use, has an improved shape and a texture of flexibility ideal for optimizing and making reliable the electrical contacts between an electrode and epidermal support.

25The geometry of the contact pad according to the invention makes it possible to maintain, protect and diffuse the conductive gel between the electrode and the scalp. The geometry of the inward-facing lip envelope provides a self-supporting cushion effect (such as the skirt of a hovercraft) and the pressure exerted on the electrode is distributed over the entire volume of gel, which allows ensure comfort and optimize conductivity. Indeed, the shock-absorbing effect of the 30 gel cushion keeps optimal contact even during patient movements.

The geometry of the contact pad according to the invention thus makes it possible to improve the location accuracy of the electrode and thus the efficiency of the device.

The flexible and waterproof nature of the elastomer guarantees protection against drying out and the external environment.

The elastic nature of the elastomer also allows it to be placed on the electrode by simple "clipping" without the use of an additional fixing element, which also makes it possible to hold the electrode in the buffer by tightening. elastic.

The interior volume of the envelope allows the maintenance of a sufficient quantity of gel to ensure optimal conductivity for the duration of the examination.

Preferably, the contact pad according to the invention may be provided with an additional elastomer structure in the concave lower part exerting local differential pressures on the epidermis, for example an internal membrane pierced with holes and furnished with flexible pins. .

The purpose of these flexible pins is to exert slight differential pressures on the skin. By this massage action they make it possible to accentuate the subcutaneous blood microcirculation and by mechanical action on the tissues to improve the penetration of the gel; this increases the local electrical conductivity of the epidermis.

Since dry hair or hairs are not conductive of electricity, these flexible pins also have the role of spreading the hair or hairs which can be crushed in a thick sheet under the electrode and therefore of facilitating the flow of the gel towards the skin.

In the same way, said additional elastomer structure can be formed of concentric rings (or concentric lips) mounted on a membrane pierced with holes, or any other elastomer structure making it possible to exert local differential pressures on the epidermis.

The simplicity and speed of disassembly and replacement allow cleaning of the electrodes and the change of flexible contact pads between each examination.

The smooth and flexible surfaces of the contact pads are easy to clean with soapy water and can be rinsed with plenty of water to remove all traces of gel and soiling.

The elastomer used, in particular silicone, supports sterilization by autoclave and contact with disinfectant products used in hospitals. The contact pads according to the invention can therefore be replaced between each examination, cleaned and dried in batches and reused for conventional examinations or in sterile environments, which makes it possible to guarantee hygiene compatible with medical or veterinary use.

5The elastomer can in particular be chosen from silicone elastomers of medical grade meeting the standards in force, for example the silicones used for the manufacture of bottle teats, sucking devices for infants, menstrual cups, respiratory masks.

The medical grade silicones are generally grouped into three categories: non-implantable, short-term implantable and long-term implantable. Materials approved in Class V and VI can be considered medical notes. Most medical grade silicones are certified at least Class VI. Silicone suppliers and some silicone prototyping companies provide guidelines for the use of the equipment.

Due to their inherently low toxicity, pure silicones pose a low risk of adverse biological reactions, and therefore have gained industrial and medical recognition.

The contact pad according to the invention, in addition to its previously described functions, can be of a nature to conduct electricity.

It is thus possible to envisage depositing a layer of flexible conductive resin on the surface of the elastomeric pad, which is compatible with medical or veterinary use.

It is also possible to choose an elastomer which itself has conductive properties, while remaining compatible with medical or veterinary use.

Another variant of conductive pad can use flush microfibers or nanofibers, the conductive micro-fibers or nanofibers being homogenized in the elastomer mass before molding. The nature of the conductive microfibers must remain compatible with medical or veterinary use, for example silver or carbon nanofibers can be used.

In one embodiment, the contact pad according to the invention may comprise an element playing the role of central valve and a pierced membrane which can be mounted on an electrode with a hole in the center. The objective of this embodiment is to be able to re-inject conductive gel, with a check valve effect. The contact pad according to the invention can thus comprise a central pin (having the function of a non-return valve previously mentioned) held by a pierced membrane. The pin, preferably conical or spherical, allows the injection of gel through the central bore of pierced electrodes, without moving the electrode. Under the effect of the injection pressure, the pin backs off because the membrane undergoes elastic deformation; the return of the gel through the injection orifice is automatically blocked by the non-return effect of the elastic pin after the gel injection is complete.

The contact pad according to the invention, made of elastomer, preferably silicone, may be provided with an internal membrane (17) pierced with holes and furnished with flexible pins (16).

The elastomer contact pad according to the invention is produced by injection, by vulcanization or by 3D printing of the elastomer and any other elements (particles, microfibers, etc.).

The vulcanization is advantageously carried out inside a multi-cavity mold produced so as to include an upper part of a shape adapted to the profile of the electrode to be clamped and a convex lower part of geometry in accordance with the invention. After crosslinking the material, an end of the molded pad is pulled to obtain the release of the contact pad according to the invention. The elasticity of the elastomer makes it possible to produce geometries with strong undercuts which are demolded manually by elastic deformation.

The contact pads according to the invention can be manufactured by injection on a press adapted to the chosen elastomer.

Preferably, the contact pads according to the invention are produced by vulcanization or hot compression of an elastomer (for example silicone rubber) in a multi-imprint mold.

In another embodiment, the contact pads are produced directly by means of three-dimensional printing (called 3D printing).

The dimensions and the shape of the contact pad (and therefore of the mold used to manufacture it if necessary) are advantageously chosen so as to be adapted to the usual electrodes, usually used naked or well equipped with textile dollies.

However, in order to allow flexibility in use, the contact pad according to the invention may include, as described above, a mounting interface made of plastic or biocompatible conductive material allowing adaptation to other types of electrodes.

A geometry and a specific holding interface also make it possible to adapt the invention to the cup-type electrodes.

Several contact pads according to the invention can be networked and linked together by an elastomeric membrane, for example to form a plate of said contact pads, a flexible cap provided with said contact pads.

applications

These electrodes can be used in the context of diagnosis or stimulation in the medical or veterinary field, such as ECG electrocardiograms, EEG electroencephalograms, EMG electromyograms, but also in the framework of brain-machine interface ICM (robot neuro-control, vehicles, exoskeletons, software ...), in a paramedical framework in bio-feed-back and functional rehabilitation applications.

A brain-machine interface (ICM) is a direct link between a brain and a computer, allowing an individual to perform tasks without going through the action of the peripheral nerves and muscles. This type of device, as described in US Pat. No. 6,171,239 or patent application WO2003 / 037231, makes it possible to control, by thought, a computer, a prosthesis or any other automated system, without requiring its arms, hands or legs.

Claims (11)

1. Flexible elastomer contact pad (1) for an electrode for collecting an electrophysiological signal (2), said pad comprising: an upper part (12) comprising elastic clamping means (13) of said pad on said electrode, a lower part (11) of concave shape comprising a skirt (15) intended to hold in a cavity (14) an electrolyte gel cushion between said electrode and a support, said skirt being provided with a peripheral sealing lip (18) curved inwardly making it possible to ensure a tight connection of said lower part with said support. 2. Contact pad according to claim 1 wherein the elastomer is a 15grade silicone compatible with medical or veterinary use. 3. Contact pad according to one of claims 1 to 2 further comprising a mounting interface (20) of plastic, polymer or metal allowing adaptation to different types of electrodes. 4. Contact pad according to one of claims 1 to 3 comprising a central valve maintained by a perforated membrane which can be mounted on an electrode comprising a central bore to allow the injection of gel. 255. Contact pad according to one of claims 1 to 4 wherein said lower part of concave shape comprises a complementary elastomer structure making it possible to exert local differential pressures on the epidermis. 6. Contact pad according to claim 5 wherein said lower part of concave shape comprises one or more additional concentric sealing lips. 7. Contact pad according to claim 5 wherein said lower part of concave shape comprises an internal membrane (17) pierced with holes and lined with flexible pins (16). 8. Contact pad according to one of the preceding claims, in which the pad is covered on the surface with a layer of flexible conductive resin or of a conductive metal film, preferably by vapor deposition. 9. Contact pad according to one of claims 1 to 7 wherein the elastomer is a conductive elastomer, preferably an elastomer containing carbon nanowires or silver nanowires. 10. Contact pad according to one of claims 1 to 7 wherein the elastomer comprises conductive microfibers flush with the surface. 1511. Contact pad according to one of claims 1 to 10 manufactured by injection, vulcanization or three-dimensional printing. 12. Device for medical or veterinary use for electrophysiological examination comprising at least one electrode for collecting an electrophysiological signal and at least one buffer 20 contact according to one of claims 1 to 11 assembled by elastic clamping on said electrode. 13. Network of contact pads according to one of claims 1 to 11 connected together by a flexible elastomer membrane.