Organic humidity sensors - improvement of climatic resistance

This paper deals with research and development of humidity sensors based on organic sensitive materials. Organic sensors consist of the substrate with the electrode system covered by the thin sensitive organic layer. The base substrate consists of 99% alumina. Golden electrodes have the interdigital form with the isolation gap 25 μm wide and finger 25 μm wide. Organic material is applied on the substrate by the spin coating. The main work was focused on the environmental stabilization of organic sensor layers. Research in organic sensitive materials stabilization was performed on molecules known as phtalocyanines which shows a high sensitivity to the humidity but insufficient climatic resistance. The stabilization was performed in two ways. The first way is to use polymer matrix where the phtalocyanine is fixed. The second way is to use passive protective layer covering the phtalocaynine layer in the second case. The best results were obtained for polystyrene protective layer. The sensor with polystyrene protective layer shows an adequate stability even at the water resistance test, almost the same impedance-humidity characteristic, similar sensitivity and the response time.