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In this study, a simple thick-film humidity sensor was fabricated by coating wet-synthesized ZnO nanorods on screen-printing interdigitated electrodes. We investigated the influence of the coating procedure on the microstructure of ZnO nanorod films and thereby on humidity sensing. The experimental results revealed that the specific surface area (SSA) decreased and the average pore size (APS) increased with increasing the sintering time and the number of coating layer. The humidity response depended significantly on the pore properties of the ZnO nanorod films. By virtue of the incipient wetness analysis, it was found that the adsorption of water molecules on the ZnO surface led to the decrease in electrical resistance even though the ZnO was rod like, n-type semiconductor. While tuning the pore structure of the ZnO nanorod film, the thick-film humidity sensor might display near-linear response in the full range of 0%-100% relative humidity (RH). [ABSTRACT FROM AUTHOR]