Quartz crystal microbalance humidity sensor with porous electrodes

This short paper describes a new idea for humidity measurement using QCM (Quartz Crystal Microbalance) devices. It is based on an etching approach which produces micropores into the electrodes of a QCM, instead of the common approach of coating the electrodes with hygroscopic materials. The electrodes are etched wet-chemically using buffered king water (NHO/sub 3/:HCl=1:3). The electrode surface becomes rough, resulting in a large surface area for water adsorption. Photolithographic etching using a plasma will be the next research stage, this will eliminate the generation of a randomly dented surface, hence providing a uniform porous structure. Fabrication and results of preliminary measurement are described in this paper.