Abstract: Disclosed is a method of providing a substrate with a layer comprising a polyvinyl base hydrogel and a biochemically active material by photolithograhy, comprising coating the substrate by centrifugal force with an aqueous solution of a photosensitive hydrogel forming polymer, a crosslinking agent and a biochemically active material, drying said coating, exposing the coated substrate through a photomask to ultraviolet radiation and developing said exposed coating, which is characterized by applying to the substrate an aqueous solution comprising as the cross-linking agent a polyazonium compound and glutardialdehyde. Because of this specific combination of cross-linking agents superior properties with respect to the binding of the biochemically active material are obtained.

Abstract: For a potentiostatically operable, polarographic-amperometric sensor, in particular for biomedical use, wherein a working electrode (5) and a reference electrode (4) are covered by an electrolyte layer (9) which is separated from the medium to be measured by a semipermeable membrane (8), the invention proposes to provide the counter electrode (6) in the form of an external electrode which--for example--can be an outer metal coating surrounding the sensor chip (2) in a three electrode system fabricated as micro-sensor with the integrated technique, and which can be made--for example--of a stainless steel material or of a conductive plastics material.

Abstract: An electro-chemical cell for determining a particular property or component of a fluid includes a cathode electrode, an anode electrode spaced from the cathode, an electrolyte filling a space containing the cathode and anode electrodes, a selectively permeable membrane separating the electrodes and the electrolyte from the fluid to be analyzed and a layer of a hydrophylic polymer provided between a membrane and the electrodes and covering at least the cathode wherein the membrane has at least one hole in it for allowing electrolytic component of the fluid to enter the hydrophylic polymer layer and that the distance between the holes and the membrane and the cathode is relatively large as compared to the width of the cathode.