Low-cost inkjet-printed humidity sensor using nanoporous surface on coated paper

The present work describes the behaviour of nanoporous structure on two coated papers for determining their suitability for relative humidity measurement. We found that the paper with smaller pore size was better in terms of response and relative humidity range. The nanoporous inorganic thin film with high surface to volume ratio is better to detect the presence of water molecules in the environment. The hydrophilic nature of the surface coating is thus found more active compared to cellulosic paper for sensing water vapour. Prototype sensors made by us responded to the whole range of 15% 92% RH by combining the resistance and capacitance variations of the interdigitated electrode. The resistance variations provided better response over the range of 15% 55% RH whereas capacitance variation was better in 55% 92% RH. The novelty of the present work is using nanocoated papers which are low cost and bio-degradable for field applications.