Inkjet printing on paper for the realization of humidity and temperature sensors

We report on inkjet printing of silver nanoparticles on paper for the design of resistive temperature and capacitive humidity sensors. Temperature and humidity have shown to have an influence on the electrical and mechanical properties of the Ag printed structures on paper. The passivation of the paper substrate and the Ag structures with parylene was investigated to reduce these effects and improve the stability of the structures. The lines were printed with an average thickness of 0.8 μm and a resistivity of 30 μΩ•cm. The Ag thermometer coated with parylene showed a good linearity with a TCR of 0.0011°C-1, while the capacitive humidity sensor exhibited an exponential response. This study foresees the possibility of using paper as substrate with inkjet printing of materials for the design of low-cost environmental sensors.