Working electrode printed on a substrate

1. A device comprising:

a substrate;

an electrode;

a track; and

a recess, wherein the substrate extends over a first thickness, between a first face and a second face, wherein the electrode is printed on the first face, wherein the track is printed on the second face,

wherein the substrate is electrically insulated,

wherein the electrode is conductive to electricity essentially through carbon particles,

wherein the track is conductive to electricity and contains particles of silver,

wherein the recess is conductive to electricity and is made of an ink which comprises a binary mixture of carbon and silver in proportions where the quantity of silver divided by the sum of the quantities of carbon and silver present in the binary mixture is comprised within a 0 to 1 interval,

wherein the recess extends within the substrate from the first face to the second face,

wherein the recess is in electrical contact with the electrode at the level of a first junction located on the first face,

wherein the recess is in electrical contact with the track at the level of a second junction located on the second face, and

wherein the linear density of silver particles in the recess at the level of the first junction, perpendicularly to lines of a current passing through the first junction, is lower than the linear density of silver particles in the track at the level of the second junction, perpendicularly to lines of a current passing through the second junction.

2. The device according to claim 1 , wherein the recess is conductive to electricity essentially through carbon particles.

3. The device according to claim 1 , wherein the recess has a concentration of silver particles essentially equal to the concentration of silver particles of the track and wherein the section of the recess, parallel to the first face, at the level of the first junction, has an area lower than that of the section of the recess, parallel to the second face, at the level of the second junction.

4. The device according to claim 2 , wherein the recess extends, within the substrate, according to a rotation cylinder around a cylindrical axis perpendicular to the first face.

5. The device according to claim 2 , wherein the recess extends, within the substrate, according to a truncated cone around an axis perpendicular to the first face, the section of the truncated cone, parallel to the first face, decreasing from the second face to the first face.

6. The device according to claim 2 , wherein the recess extends, within the substrate, according to a truncated cone around an axis perpendicular to the first face, the section of the truncated cone, parallel to the first face, decreasing from the first face to the second face.

7. The device according to claim 3 , wherein the recess extends, within the substrate, according to a truncated cone around an axis perpendicular to the first face, the section of the truncated cone, parallel to the first face, at the level of the first junction, having a surface lower than the surface of the second junction.

8. The device according to claim 1 , wherein the recess includes a part printed on said second face, up to the second junction.

9. A method of manufacturing a device according to claim 1 , comprising:

drilling a hole through said substrate from said first face to said second face;

filling the hole with said ink to form said recess;

printing, on the first face, said electrode, in electrical contact with the recess; and

printing, on the second surface, said track, in electrical contact with the recess.

10. The device of claim 1 , wherein the device is used as a working electrode of an electrochemical cell.