DD222205A1 - CONTACT BODY FOR ELECTRODES AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Abstract

The invention relates to a contact body for electrodes which serve to decrease electrophysiological action voltages or currents from the skin surface of biological objects. The aim is to produce a Kontaktkoerpers, which has a high Leitfaehigkeit, no noticeable polarization voltage can be produced and materialoekonomisch and can be efficiently produced. The object of the invention is in such a constructive and material design of the Kontaktkoerpers that a significant reduction in the use of silver while maintaining the effective surface and secure contact for the decrease of the electrophysiological action signals is made possible. According to the invention, the contact body is formed as a prismatic base body of electrically nonconducting material (plastic or ceramic) whose surface has micropores in which a silver layer partially or completely enclosing the base body is anchored, the surface of which is at least partially converted into a silver halide film. The invention can be applied in the field of medical technology, biophysics and biotechnology.

Description

Contact body for electrodes and method for its production.

Field of application of the invention

The invention can be applied in the field of medical technology, biophysics and biotechnology. It relates to a contact body for electrodes, which serve to decrease electrophysiological action voltages or currents from the skin surface of biological objects and a method for producing such a contact body.

Characteristic of the known technical solutions

Electrophysiological action signals of living organisms are directed from their place of origin by means of ion conduction within the tissue fluid to the body surface, from where they can be removed with the aid of electrodes. The different layers of tissue represent a resistance to the signal, so that only a fraction of the signal amplitude is applied to the body surface. Therefore, it is necessary that the electrodes for taking the signal have a stable electrode potential, low impedance and low noise.

These requirements are the known electrodes of gold, platinum, tungsten, molybdenum, copper, stainless steel, titanium u. a. only partially fair, since considerable potential fluctuations occur, which are very disturbing, especially in long-term monitoring.

Improved electrodes, the contact bodies are pressed from silver powder and silver chloride (ζ B. DE-OS 24 49 091) j do not have this laughing part, because the reaction '

Ag Cl + e Ag + Cl ι

stable and reversible. But they have the defect that the generation of a uniform silver chloride film on the surface of the contact body is uncertain »Furthermore, the high price due to the relatively high proportion of silver as well as the complex production technology economically disadvantageous»

The latter disadvantage is also exhibited by contact bodies produced by pressing titanium hydride with silver chloride and basic metal salts. In addition, contact bodies containing alkaline salts can lead to undesired reactions with the acid mantle of the skin or the coupling electrolyte.

To improve the material economy, it has also been proposed to produce the contact body at least partially from non-conductive material (DE-OS 28 02 538). In this case, a non-woven textile material is used, which is rolled in silver powder. The desired silver silver chloride contact with the skin is achieved by means of a gel containing chloride ions. A disadvantage must be considered that due to the low adhesion of the silver powder on the textlien structure only a very loose silver layer is formed and thus a secure contact, especially in the edge zone is not guaranteed.

Aim of the invention

The aim of the invention is the production of a contact body for electrodes, which has a high conductivity, does not give rise to appreciable polarization voltage and can be produced economically and rationally »

Essence of the invention

The object of the invention consists in such a constructive and material design of the contact body that a substantial reduction of silver use while maintaining the effective surface and secure Kontaktgäbe for the decrease of the electrophysiological action signals is made possible, and in a corresponding manufacturing process,

Starting from the prior art, silver and a silver salt were selected as the contact material, wherein the contact body is formed in the interior as a prismatic, preferably cylindrical furfniger body of electrically non-conductive material.

According to the invention, the non-conductive material used for the base body is plastic, preferably ABS plastic, or ceramic whose surface has micropores in which a solid or partially enclosing solid silver layer is anchored whose surface is at least partially converted into a silver halide film. The silver layer preferably has a dendritic crystal structure. In the method according to the invention for producing the contact body, a base body is first brought into the described form by casting, pressing or sintering, depending on the type of material used. Subsequently, the base body is exposed to a mordant for cleaning and conversion, whereby in particular a Hydrophilmachung and a roughening or detachment of microscopic parts takes place from the surface. The subsequent treatment of the base body with a noble metal solution causes activation of the prepared surface for subsequent autocatalytic silvering. The preferably dendritic crystal growth resulting from the autocatalytic deposition of silver realizes a large effective surface area and a very strong anchoring of the silver layer ^N in the

'Micropores of the body.

As the last process step, the silver-plated base body is exposed to a halide ion-containing, preferably chloride-containing, medium. As a result, the surface of the silver layer is at least partially converted to silver halide, in particular at the ends of the dendritic crystals.

embodiment

The invention will be explained in more detail by the following examples for the embodiment of the method. "

Example 1:

From ABS plastic material are basic body parts with

   .- 2 -

625 mm thick ", they are then pickled in ABS pickling and rinsed in Sn (II) saline solutions. The activated in ammoniacal 'silver salt solution moldings are silvered autokalytisch 75 three times successively each minutes at 65-2 C in 200 ml of a chemically reductive silver solution of the following composition ^s ·

Potassium silver cyanide 0.01 mol / l

Potassium hydroxide 0.01 mol / l

Potassium cyanide 0.05 mol / l

Formaldehyde. 0.2 mol / l

Uonylphenol 2 mg

The deposited silver amount per molded part is about 17 mg ₉ which corresponds to a mean layer thickness of about 2.3 / utn. Subsequent chemical or electrochemical treatment in a halide ion-containing solution produces a silver halide film on the silver surface. ,

example 2x

The moldings produced as in Example 1 are rinsed activated after pickling in palladium solution and silvered three times 30 minutes successively in the following solution at 60-3 C autocatalytically.

Potassium silver cyanide 0.004 mol / l

Potassium hydroxide 0.002 mol / l

¹ potassium cyanide 0.002 mol / l

Formaldehyde. 0.02 mol / l

_Λ nonylphenol 1 mg / 1

The deposited amount of silver, per molding is in this case 9 mg, which corresponds to a mean layer thickness of 1.2, to. By "subsequent chemical or electrochemical treatment in a halide ion-containing solution, a silver halide film is formed on the silver surface."

Example 3;

The corresponding parts for the basic body can also be made by sintering of ceramic, z. B. unglazed porcelain. Wake the pretreatment with a suitable mordant the process can be carried out analogously to the above.

Claims (3)

Κ / claim for invention. ; 1 "Contact body for electrodes ^ which serve to decrease electrophysiological action voltages or currents from the skin surface of biological objects and as Contact material silver and a silver salt, wherein the contact body in the interior as a prismatic, ;; preferably cylindrical base body is formed of electrically non-conductive material, that * ; by ge characterize t _ιΤιι that as a non-conductive material for the green body plastic, preferably ABS plastic, »material, or ceramic is used, the surface of which has micropores, in which a body partially or completely enclosing solid silver layer is anchored whose surface is at least partially converted into a silver halide film». · '. · '. \. , ". 2 "Contact body according to item .1, characterized in that the silver layer preferably has a dendritic crystal structure ,, - 3 · A process for preparing a contact body for electrode using silver, characterized _iu gekennzeichnetj that a base body by casting, pressing or sintering is formed of nonconductive material, is then exposed for cleaning and conversion of the surface of the base body a mordant, then with an activating Treated noble metal solution, silvered autocatalytically and halo genigenionenhaltigen, preferably containing chloride ion, medium is exposed »