Thin-film Clark-type oxygen sensor based on novel polymer membrane systems for in vivo and biosensor applications

A planar miniaturized Clark-type oxygen sensor based on the Ross principle has been produced by means of thin-film technology. The use of a polarizable counter electrode in a three-electrode configuration allows the regeneration of the cathodically consumed oxygen, resulting in a zero-flux amperometric oxygen sensor. The platinum working and counter electrodes and the Ag/AgCl reference electrode were covered with a photostructured hydrogel layer, forming the electrolyte compartment, and a photostructured hydrophobic gas-permeable membrane. This arrangement exhibits no oxygen consumption and therefore the signal of the sensor shows almost no flow dependence. Additionally, this electrochemical feature leads to a dynamic equilibrium of the reaction products in the hydrogel layer, overcoming the lifetime limitations caused by buffer degradation in the classical Clark principle. The sensor was tested in buffer solutions and bovine serum, showing excellent performance and no effects of fouling on sensor response. This device can be scaled down and is best suited for integration with other sensors and as a basic transducer for biosensors.