Abstract: A porous poly(2-acryl-amido-2-methyl-propane sulphonic acid)-based humidity sensing element is disclosed which provides improved range of humidity measurement and response time with little or no hysteresis. It includes: (a) a non-conductive substrate which has a pair of electrodes formed thereon; (b) a porous poly(2-acryl-amido-2-methyl-propane sulphonic acid) film formed on said electrodes. The porous poly(2-acryl-amido-2-methyl-propane sulphonic acid) film is formed by first forming a non-porous poly(2-acryl-amido-2-methyl-propane sulphonic acid) film on the electrodes, then subjecting the non-porous poly(2-acryl-amido-2-methyl-propane sulphonic acid) film to a heat treatment at temperatures between about 170° C. and 240° C. such that a porous structure is formed in said poly(2-acryl-amido-2-methyl-propane sulphonic acid) film.

Abstract: A method for forming a solid state humidity sensor is disclosed which comprises the steps of: (a) dissolving a tungstate salt into an aqueous solution; (b) adjusting the pH of the aqueous tungstate salt solution to below 8.5; (c) forming one or a pair of electrodes on an insulating substrate; (d) placing the substrate into the pH-adjusted aqueous tungstate salt solution and heating the aqueous solution containing the substrate at temperatures above 70.degree. C. to thereby form a pyrochlore-type crystalline tungsten trioxide film over the electrode or pair of electrodes; and (e) forming another electrode over the pyrochlore-type crystalline tungsten trioxide film if only one electrode is formed during step (c).

Abstract: A method for forming a solid state humidity sensor is disclosed which comprises the steps of: (a) dissolving a tungstate salt into an aqueous solution; (b) adjusting the pH of the aqueous tungstate salt solution to below 8.5; (c) forming one or a pair of electrodes on an insulating substrate; (d) placing the substrate into the pH-adjusted aqueous tungstate salt solution and heating the aqueous solution containing the substrate at temperatures above 70.degree. C. to thereby form a pyrochlore-type crystalline tungsten trioxide film over the electrode or pair of electrodes; and (e) forming another electrode over the pyrochlore-type crystalline tungsten trioxide film if only one electrode is formed during step (c).

Abstract: A gas sensor that has its heater and sensing layer on opposite sides of the substrate. The gas sensor includes a buffer layer separating the gas-sensing layer from the substrate to improve mechanical strength and electrical properties. The heater is preferably formed of nickel paste and is provided on the back of the substrate.

Abstract: A method of fabricating a gas sensor which comprises a substrate; a buffer layer coated on the substrate; at least one gas sensing layer arranged on the buffer layer; a pair of electrodes disposed on the gas sensing layer; and a catalytic layer coated on the gas sensing layer. A spin coating process is performed, using centrifugal force, to form the layers which are thin and evenly deposited on the substrate. The gas sensing layer of the gas sensor is formed before forming the electrodes of the same such that the heat treatment thereto can be carried out at 800.degree. C. which is much higher than the conventional temperature of 600.degree. C. The bonding of the gas sensing layer to the substrate is thereby much stronger than the conventional gas sensor.