WO2008096332A1

WO2008096332A1 - Inhomogeneous gel

Info

Publication number: WO2008096332A1
Application number: PCT/IB2008/050484
Authority: WO
Inventors: Félix Buhlmann; Klaus SCHÖNENBERGER
Original assignee: Compex Medical S.A.
Priority date: 2007-02-09
Filing date: 2008-02-11
Publication date: 2008-08-14

Abstract

The gel layer for electrodes has different electrical properties in different geometrical directions.

Description

INHOMOGENEOUS GEL

The present invention concerns an inhomogeneous gel for use with electrically active zones, for example stimulation electrodes.

In the following description, one will use the word "electrode" to identify the general notion of "electrically active zone".

In the field of stimulation, sensing or recording electrodes, one often uses in the design of such an electrode a layer of gel which improves the electrical and mechanical contact of the electrode to the portion of the skin on which the electrodes is applied

When several electrodes are to be applied at the same time and close to each other, it is much more convenient for the user if those electrodes are made or placed on a single insulated substrate, for example a fabric, with several electrical disjoint active surfaces.

Normally, the best solution is to apply gel only under the active surfaces of the electrodes to be sure that the current really flow through the skin rather than through the gel without penetrating the skin.

However, such electrodes are difficult to fabricate and more expensive.

A simple and cost effective solution to decrease the fabrication costs is to apply the gel on the entire surface of the electrode support (typically a fabric).

According to the present invention in order to force the stimulation current to penetrate into the skin 4 rather than remain in the gel layer between the electrodes the idea is to provide a gel layer 1 that has different electrical properties is different geometrical directions. This is represented in figures 1 and 2, where the gel layer 1 is placed under electrodes 2. The electrodes 2 have a length 1, a width h and are separated by distance d. The thickness of the layer is e.

As shown in figure 2, to obtain the desired effect, the resistance in the direction Rxy must be higher than the resistance in the direction Rz.

Rz w pgel x e/lh and Rxy « pgel x d/el

One thus wishes Rxy/Rz = dh/e² » 1

In another embodiment represented in figure 3, one can introduce a barrier 3 (or isolation) in the gel layer to obtain the effect. For example, the barrier may be placed in the mould when preparing the gel layer.

Other equivalent embodiments and means are of course possible within the scope of the present invention in order to obtain the desired result.

Such a gel layer may typically be used in stimulation system with electrical stimulators.

Claims

1. A gel layer (1) for electrodes (2) wherein the layer has different electrical properties in different geometrical directions.

2. A gel layer (1) as defined in claim 1, wherein the resistance in the direction Rxy is higher than the resistance in the direction Rz.

3. A gel layer as defined in one of the preceding claims, wherein Rxy/Rz = dh/e² » 1

"d" being the distance between electrodes (2), "h" the width of an electrode (2) and "e" the thickness of the layer (1).

4. A gel layer (1) as defined in claim 1 wherein it comprises isolating means between two neighboring electrodes (2).

5. A device comprising at least one electrically active zone and a layer as defined in one of the preceding claims.

6. A stimulation system comprising at least a layer as defined in one of claims 1 to 4 or a device as defined in claim 5 and a stimulator.